[Buildbot] #3529: Add warning in trigger step if collapseBuild=True for the target builder

[Buildbot trac]

#3529: Add warning in trigger step if collapseBuild=True for the target builder
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Reporter:  tardyp       |       Owner:
    Type:  enhancement  |      Status:  new
Priority:  major        |   Milestone:  0.9.+
 Version:  master       |  Resolution:
Keywords:               |
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Changes (by rutsky):

 * milestone:  0.9.0 => 0.9.+


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Ticket URL: <http://trac.buildbot.net/ticket/3529#comment:2>
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